In recent years, it is general to mount imaging apparatuses on mobile phones, smartphones, tablet terminals, personal computers, and the like. In the imaging apparatuses, imaging elements such as charge coupled device (CCD) image sensor and complementary metal oxide semiconductor (CMOS) image sensor are used. In such mobile phones, smartphones, and the like, image processing is commonly used for digital zooming, to implement a digital zooming with a higher magnification, a long focal length lens disclosed in Patent Document 1 can be used as an imaging optical system.
Patent Document 1: Japan Patent Publication No. 2016-114803.
However, the long focal length lens disclosed in Patent Document 1, as a long focal length system lens conventionally used in the mainstream digital zooming system together with a wide-angle lens, has a field angle structure that has to be broadened. Therefore, when the digital zooming is performed, increasing the zooming magnification can cause problems of thicker pixels and significantly deteriorated image quality.